The Ways of Reason

This dissertation is about rationality, both practical rationality , and theoretical rationality . I argue that there are interesting similarities as well as interesting differences between practical and theoretical rationality. One of the similarities is that both of them are essentially related to the explanation of actions and beliefs, and one of the differences is that whereas theoretical rationality has the hyper-external aim of truth, practical rationality has the non-hyper-external aim of desire satisfaction. ;In chapter 1 I present a general framework for the development of theories of rationality, and in chapter 2 I apply that framework to practical rationality. The result is an instrumentalist view of practical rationality. In chapter 3 I discuss the relation between practical rationality and morality, and I argue that one can be an instrumentalist about practical rationality without being a subjectivist about morality, even while accepting plausible forms of motivational internalism. In chapter 4 I argue that theoretical rationality is not reducible to practical rationality. In chapter 5 I apply the framework of chapter I to theoretical rationality, and the result is a theory with both internalist and externalist components. In chapters 6 through 8 I defend that theory from some of the main objections that can be leveled at it, such as the objection from disjunctivism and the "new evil demon problem"